Health means that one has no illness. Moreover, someone is only healthy if he or she is generally well, both in terms of the body and the mind and soul. There are different opinions about what exactly health means.
The World Health Organisation has defined exactly what it means by health: "Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity." So what matters is how healthy you feel yourself to be. This also includes feeling good about the people you often meet. For example, being bullied at school does not make you feel healthy in a comprehensive sense.
From a medical point of view, many people are ill because they have cancer, for example. But as long as one does not notice this cancer, he can consider himself healthy, as long as he can do the most important tasks in life.
Good for health are proper food and exercise. If you always eat bad things or exercise little, you can get sick more easily. Good health also includes having good contacts with other people. Too many hours on the computer or smartphone are bad for your health. But you can also be healthy and disabled at the same time: Being blind or in a wheelchair does not make you ill.
The many people, facilities and buildings that are there for health are called the health service. Doctors and hospitals come to mind first. Then there is care: carers such as geriatric nurses help the sick, the elderly and the disabled who cannot help themselves. Certain insurance companies are also part of the health system, especially the health insurance companies.